Killer and Zoro share a number of similarities, including their inclination towards killing/violence, status as the only non-captain Supernovas, lack of an apparent position in their crew, a fighting style that includes blades, and the only two who hold no apparent Devil Fruit abilities.

After the timeskip, Killer’s bounty has been raised from 162,000,000 to 200,000,000

In the 5th fan poll, Killer ranked 60th.

As stated in SBS, Killer eats with his mask on, and prefers food he can consume through the holes of his mask (stick-shaped or foods such as ramen). His meals have pasta as main every day and his favorite is Aglio e Olio. He also drinks alcohol through a straw. His stated preference for remaining masked while eating ascended from trivia to a known fact when he did just that in Chapter 793. In the picture below you can see Killer eating carrot and cucumber sticks.

Killers shares the same birthday with Vivi (February 2).

Oda said he picked the name “Killer” out of sheer laziness; thus the name holds little to no meaning. It means that he is the only Supernova introduced in the Sabaody Archipelago Arc whose name is not linked to a real life pirate or privateer and the only one of the group with no other meaning at all.

His favorite food is peperoncino, and his least favorite is curry udon.

What I basically think is that Zou is now the first arc of a new saga with a new focus.
The “Pirate Alliance” saga is now over, we got our alliance and I think that the next arc which is the Reverie/Revolution Arc which I mentioned in my “History of the Revolution” arc is going to feature Sanji as it’s main character.
So as Doflamingo mentioned- the Throne Wars are coming and it’s big players- the pirates (Yonko, Shichibukai, Worst Gen), “Forces of Justice” (CP, Kaigun), and the RA will now begin to engage in different combats and the victor would be the one gaining the dominance eventually.

Now that there are a lot of revolutions due to Doflamingo’s downfall at the hands of Luffy, as mentioned by Dragon, and for that reason he now wants to assemble the “Intense” leaders of the RA (Which as mentioned above I believe includes Inuarashi and Nekomamushi), possibly for the strike that he plans during the Reverie which is nigh:

Now it seems reasonable that the message should arrive as soon as possible, and considering the height of Zunisha it seems reasonable that the messenger could be the same one that took Sabo away is chapter 794, the one that is/controls the Crows (Which some believe to be the same one in the silhouette shown above, but no evidence for that):

However, he came only to find Inu and Neko out-cold and severed, however Sanji was there as well.

The RA has already shown impressive amounts of knowledge, indicating that whatever Sanji has with his past, they might know that so the Crow-Man might have decided to ask him to perhaps help them locate the, what I believe to be a secret weapon, to both have more fire-power and to prevent the WG to take hold of Sanji, and the information, first.

Sanji agreed, after all the WG have done to him, and still does want to, as well as for his nakama’s sake to help the RA on this case so he wrote a letter for his nakama where he promises them to return.

Afterwards we might get the Revolution Arc, where we might receive a lot of new pieces of information- both regarding the Void Century, we’ll get Sanji’s past, we’ll know a lot about the Revolutionaries and most notably Dragon and we’ll see many characters return in the Reverie.

After all that the world of One Piece would change forever!

So hope you like that idea- I know it’s not as serious and specific as other theories of mine but I decided it was worth writing.